Evaluation of pea germplasm for resistance to powdery mildew (Erysiphe pisi) and inheritance of resistance

Powdery mildew of pea caused by Erysiphe pisi DC ex. Saint-Amans is one of the most destructive and widely prevalent diseases in Himachal Pradesh both during main and off- season. The study of identification of resistant sources and inheritance of resistance are most important for breeding resistant varieties. Currently there is no stable source of resistance (commercial cultivars) available against this disease so 317 pea germplasm lines were screened under natural epiphytotic conditions. Out of 317 pea lines only 6 genotypes i.e. DPP 362, JP-501-A/2, DPP-1542EP, PMR-21, KMNR- 894 and JI-1766 exhibited highly resistant reaction against powdery mildew and 59 cvs./Lines were moderately resistant. In order to study the genetics of resistance in pea, 6 lines showing resistance to different races of Erysiphe pisi viz., JI-1559, JI-2480, IPF- P- 2–5, DPP-13, DPP-25G, DPP-1542 EP along with susceptible line ‘Lincoln’ were crossed in diallel mating design. Crosses made either with or on Lincoln gave highly susceptible reaction. Crosses made between resistance to resistance -or resistant to moderately resistance showed either resistant or moderately resistant or moderately susceptible reaction. Segregation pattern of F₂ population of six crosses under field conditions revealed a ratio of 1 resistant to 3 susceptible (1:3) in different crosses, thereby indicating the presence of single recessive gene in the donor parents. In vitro evaluation of F₂ under green house condition on the detached leaves with four powdery mildew isolates also exhibited a segregation ratio of 1 resistant to 3 susceptible (1:3) in F₂ population of each cross thus further established that resistance in genotypes JI-1559, JI-2480, IPF- P- 2–5, DPP-13, DPP-25G and DPP-1542 EP is governed by single recessive gene.